Preheat oven to 350 degrees. Lightly grease a muffin tin or cupcake molds and set aside.
Melt butter in a medium saucepan over medium heat.
Stir in the flour and cook for a minute or so.
Gradually add milk, stirring until well blended.
Continue to cook and stir until the mixture comes to a boil.
Remove from heat and add the cheese, stirring until it has melted.
Stir in mustard and veg.
Whisk the egg yolks until well beaten, then temper them with the batter one spoonful at a time. Once they’re warm, pour the yolks into the batter a bit at a time, making sure they’re completely whisked in.
Beat egg whites with a mixer until peaks are stiff but not dry, about 5 minutes.
Gently fold whites into yolk into the souffle batter..
Pour into muffin pan or cups.
Bake for 25 minutes or until the souffles are puffed and set. Try to avoid opening the oven door. The souffles are still delicious even if they fall, but they don’t look as pretty.